<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>computed</title>
    <script src="Vue/vue.js"></script>
    <script src="Vue/vue-router.js"></script>
</head>
<body>
<div id="compute">
    <div>
        <input type="text" v-model="a">
        <label>*</label>
        <input type="text" v-model="b">
        <label>=</label>
        <input type="text" disabled v-model="c">
    </div>
</div>
<script>
    var vue=new Vue({
        el:"#compute",
        data:{
            a:"",
            b:"",

        },
        computed:{
            c:function () {
                    return  Number.parseFloat(this.a) *  Number.parseFloat(this.b);
            }
        }
    });
</script>
</body>
</html>